1. Field of the Invention
The present invention relates to deflection yokes and, more particularly, to a mounting device provided on the coil separator of such a deflection yoke for allowing a frame correction means to be easily and precisely mounted to the coil separator of the deflection yoke.
2. Description of the Prior Art
As well known to those skilled in the art, deflection yokes for CRTs (cathode ray tubes) of TV receivers or computer monitors have been typically classified into a plurality of types, for example, saddle-toroidal type yokes and saddle-saddle type yokes.
As shown in FIG. 1, a deflection yoke 10 is typically mounted to the neck part 2 of a CRT 1. Such deflection yokes 10 are generally classified into two types, or saddle-saddle type deflection yokes of FIGS. 2 and 3 and saddle-toroidal type deflection yokes of FIGS. 4 and 5, in accordance with a coil structure.
Such a deflection yoke 10 is used for appropriately deflecting the B (blue), R (red) and G (green) light beams, emitted from a BRG electron gun 3 set within the neck part 2 of the CRT 1, upward, downward, leftward and/or rightward, thus allowing the light beams to precisely reach the desired positions on the fluorescent screen of the CRT 1 and to form a desired picture on the screen.
FIGS. 2 and 3 show the construction of a conventional saddle-saddle type deflection yoke. In such a conventional saddle-saddle type deflection yoke, a plurality of saddle-type horizontal deflection coils 12 are installed on the internal surface of the screen part of a generally conical coil separator 11 at upper and lower portions as shown in the drawings. In addition, a plurality of saddle-type vertical deflection coils 13 are installed the external surface of the screen part of the coil separator 11 at left and right portions.
A ferrite core 14, having a generally cylindrical shape, is provided on the external surface of the screen part of the coil separator 11 for correcting the magnetic field formed by the vertical deflection coils 13.
On the other hand, a plurality of coma free coils 15 are mounted to the external surface of the coil separator 11 at a position around the neck part and are used for correcting the coma formed by the vertical deflection coils 13.
FIGS. 4 and 5 show the construction of a conventional saddle-toroidal type deflection yoke. In such a conventional saddle-toroidal type deflection yoke, a plurality of horizontal deflection coils 12 are installed on the internal surface of the screen part of a generally conical coil separator 11 at upper and lower portions as shown in the drawings. In addition, a ferrite core 14, having a generally cylindrical shape, is provided on the external surface of the screen part of the coil separator 11. In addition, a plurality of toroidal-type vertical deflection coils 16 are installed on the external surface of the above ferrite core 14 at upper and lower portions.
On the other hand, a plurality of coma free coils 15 are mounted to the external surface of the core separator 11 at a position around the neck part and are used for correcting the coma formed by the vertical deflection coils 16.
However, such conventional deflection yokes have the following problems. In the case of the saddle-saddle type deflection yoke of FIGS. 2 and 3, it is necessary to mount the ferrite core 14, having the vertical deflection coils 13, on the external surface of the coil separator 11 having the horizontal deflection coils 12. However, a frame misconvergence may be easily induced in both the dimension dispersion of the ferrite core 14 and the winding dispersion of the vertical deflection coils 13 during a process of locking the ferrite core 14 to the external surface of the coil separator 11.
That is, both a misconvergence in a vertical direction and a misconvergence in a horizontal direction are formed in such a conventional deflection yoke as shown in FIGS. 6 and 7.
Such misconvergences are corrected as follows in the prior art. That is, the misconvergence in the horizontal direction may be corrected by a correction piece 20. Such a correction piece 20 is set on the rear plate 11a of the coil separator 11 as shown in FIG. 8 and corrects the magnetic field in the horizontal direction. On the other hand, the misconvergence in the vertical direction may be corrected by correcting the magnetic field in the vertical direction. Such a correction of the vertical magnetic field may be accomplished by controlling the volume of a circuit board (not shown) provided on a sidewall of the coil separator 11 or by rotating the deflection yoke 10 around the CRT 1.
In the prior art, the desired correction of the vertical magnetic field may be somewhat effectively accomplished by controlling the volume of the circuit board or by rotating the deflection yoke 10. However, such a correction of the vertical magnetic field performed by controlling the volume of the circuit board undesirably gives bad effects on the environmental magnetic field, such as the magnetic field in the vertical direction. This forces an additional correction process to be necessarily performed to correct the environmental magnetic field. On the other hand, the correction of the vertical magnetic field performed by rotating the deflection yoke 10 around the CRT 1 undesirably gives bad effects on a final processing step, or on an ITC step, thus deteriorating work efficiency during such an ITC step.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a deflection yoke, which is designed to easily correct a misconvergence in a vertical direction of a frame, and which is not rotated during a frame correction step, thus being free from requiring an additional correction step or affecting an ITC step.
In order to accomplish the above object, the present invention provides a deflection yoke, comprising: a coil separator composed of a screen part positioned around a screen of a CRT, a rear cover part extending from the screen part to the back and covering a rear portion of the CRT, and a neck part extending from the rear cover part to the back and covering an electron gun of the CRT; a plurality of horizontal and vertical deflection coils set on the internal and external surfaces of the coil separator and used for generating horizontal and vertical deflection magnetic fields; a correction means provided on the rear cover part of the coil separator and used for correcting the vertical magnetic field in addition to a frame dispersion; and a position adjusting means provided at a position between the rear cover part and the correction means and used for holding the correction means on the rear cover part while allowing the position of the correction means relative to the rear cover part to be finely and precisely adjustable.
In the above deflection yoke, the correction means comprises: two guide rails formed on the rear cover part in a way such that the two guide rails are oppositely positioned around the neck part of the coil separator, with a guide groove being axially formed along an inside surface of each of the guide rails; two correction pieces movably set in the guide grooves of the guide rails and used for correcting the vertical magnetic field in addition to the frame dispersion; and a guider connecting opposite outside ends of the correction pieces to each other into a single body.
The correction pieces are preferably formed of a metal, and the guider is preferably formed of a plastic material.
The correction pieces are integrated with the guider into a single structure by inserting the correction pieces into the guider during a molding process of forming the guider.
In the above deflection yoke, the position adjusting means comprises: a plurality of fixed teeth formed on the external surface of the rear cover part at positions around the guide rails; and a plurality of movable teeth formed on the lower surface of the correction means and used for movably engaging with the fixed teeth of the rear cover part.
The movable teeth are formed on the lower surface of each end portion of the guider of the correction means.
The rear cover part is also provided with an elastic piece at a position corresponding to the correction means, the elastic piece having an upward elasticity so as to prevent an undesirable displacement of the correction means relative to the rear cover part.
The fixed teeth are formed on the above elastic piece.